DESCRIPTION (Adapted from applicant's description): The human vaginal epithelium is located in a key anatomical location, between the external environment and protected sites in the upper genital tract, and forms a barrier to infecting pathogens. A healthy vaginal ecosystem is critical to reproductive health. Estrogen replacement therapy and many contraceptive products and devices are vaginally delivered and may affect the vaginal epithelium. Despite the importance of the vaginal epithelium in reproductive health and disease, vaginal physiology and factors affecting differentiation of the vaginal epithelium are infrequently studied, and in vitro models of this tissue have not been widely developed. The applicant has been involved since 1995 in HD33202, a clinical study that defines unexplored parameters of normal vaginal physiology, defines changes induced by common vaginal products, and investigates these products effects on susceptibility to sexually transmitted diseases. As an outgrowth of this study, the applicant has developed a model of primary cultured vaginal cells (VECs) and has performed pilot studies of bacterial adherence and the effects of exogenous estrogen on cell growth and differentiation. Her preliminary data indicate that susceptibility of cultured VEC to bacterial adherence varies with (a) morphological parameters of differentiation; (b) the expression of glycosphingolipids (GSLs), which serve as differentiation markers and bacterial binding sites; and (c) dose and timing of exogenous estrogen exposure. The goal of this Small Grant proposal is to develop this promising model for basic investigations of epithelial differentiation and susceptibility to bacterial infection, before and after in vitro exposure to hormonal and vaginal products. The applicant hypothesizes that differentiation of vaginal epithelium affects its susceptibility to infection and its response to the application of exogenous hormones and contraceptive products. The applicant will pursue the following aims: (1) Primary VECs will be grown in culture and will be further characterized for expression of differentiation markers, such as keratins, epithelial differentiation markers extensively studied in related epithelia, and selected GSLs known to be involved in bacterial adherence. Vaginal tissue sections from normal young women, collected as part of HD33202, will be stained for the same characteristics; (2) Exogenous estrogen will be applied to VECs grown in culture and parameters of epithelial differentiation, such as the expression of keratins and of GSLs, will be investigated; (3) Studies of the adherence of Lactobacilli and of bacterial pathogens such as E. coli, which may relate to risk of premature birth, will be expanded to include the relationship between expression of differentiation markers and the effect of exogenous estrogen on susceptibility to bacterial attachment. Establishing this model will open opportunities for studying numerous aspects of women's urogenital health, including testing vaginal products, probiotics, and contraceptives; understanding protective roles of organisms in the normal flora; and studying the cellular effects of hormone replacement therapy on a key target tissue, the vagina.